Project overview

(old
material - refer now to published papers)

Interferometry
has been intensively done at long wavelengths, starting
with the radio interferometers in the years 50th
since it was easier to guide radio wavelengths in cable
while keeping the phase information or using a local
oscillator and a correlator to recombine "a posteriori"
the beams over intercontinental distances. In the optical
domain a lot of work has been done at IR and near-IR
wavelengths since it was technically easier or we must
say, less difficult to recombine directly the optical
beams since the coherence length is larger and the
turbulence slower than at shorter wavelengths. Therefore,
the visible domain of the electromagnetic spectrum is not
covered at the same level than near or mid infrared. Some
very nice and important results have been however obtained
with the GI2T interferometer in south of France, the Mark
III interferometer on the Mount Wilson, USA, the NPOI
array in Flagstaff, USA or the SUSI interferometer in
Australia. In the international
competition and with the decommissioning of
interferometers like GI2T or IOTA, the era of pioneers
is now close and we can see the great development of
worldwide facilities like VLTI, KECK-I or CHARA. The
visible domain is however one of the main goal of the
future development of optical interferometry with
respect to the unique astrophysical capabilities but is
not foreseen for the VLTI 2nd generation. VEGA will clearly have the
leadership in this context but it will also be
scientifically fully complementary of our great investment
in the VLTI facility (scientific exploitation, software
development, 2nd generation instruments).

CHARA is an interferometric facility operated by the Georgia
State University in Atlanta and is located at Mt Wilson in
California. It is equipped with 6 telescopes of 1m in
diameter and arranged on a Y-shape array with baselines
ranging from 30 to 330 meters. CHARA has been developed by
the Georgia State University and is not an open facility.
The initial group has grown through selected collaborations
with teams involved in interferometric developments. It is
now a collaboration between different groups, mainly the
Observatoire de Meudon through the FLUOR instrument, the University of Michigan
through the MIRC project, the MichelsonScienceCenterUS
interferometric excellence centre) and some peoples from the
SUSI group in Australia.
During the definition of the array, CHARA was foreseen to
operate in the visible domain but the first instruments are
operating in the near-IR domain. VEGA
will finally realize CHARA’s visible goals
and propel this unique facility at the level of the
interferometer with the world’s largest spectral
& spatial resolution. Preliminary contacts have been
taken in April and September 2005. Then a small group of OCA
has visited the CHARA array in November 2005 and finally we
have been invited at the annual CHARA collaboration meeting,
which has been held in Tucson from February 20th
to 23th. During the meeting, we have had the
possibility to present and discuss our proposition and just
recently we have obtained a formal agreement from CHARA,
considering that VEGA will
be the visible instrument of the array. This agreement is
currently being written in a Memorandum of Understanding
between OCA and CHARA and we plan together the first light
for summer 2007. The CHARA staff is greatly involved in the
VEGA design and integration
and it is for us a guaranty of success. On both sides the
work has already started.